1. Field of the Invention
The present invention relates to a pallet transport system, and more particularly to a cam-controlled pallet transport apparatus that comprises individual pallets traveling in succession on a run way, each of the pallets containing a drive motor and an in-line indexing dual-plate cam mechanism rotatably fixed to the drive motor shaft, and the run way including pairs of cam followers which are arranged at regular intervals along the run way and each of which engages the corresponding plate cams on a pallet facing it. The cooperating action of the dual-cam assembly and the cam followers facing it causes the pallet to advance and then remain motionless for a certain amount of time as determined by the profile of the dual plate cams. The advance and stop operations for the pallet are repeated so that each succeeding pallet can travel on the run way in an orderly fashion without interfering with each other.
2. Description of the Prior Art
Conventional trolley (or carrier) transport employs a self-drive system in which each of individual trolleys contains its own drive motor, which engages a toothed gear, wheel or chain wheel on the trolley. The toothed gear, for example, is driven by the motor for rotation, causing the trolley to travel on a run way. In that self-driven trolley transport system, it is known that the traveling speed of the trolley is slow because of its gear meshing mechanism and the precision with which the trolley is to be stopped in position is low. For practical purposes, therefore, the application of the prior art transport system is only restricted to those installations where the precision requirements or tolerances for stopping the trolley in position are relatively generous, such as in the range of several millimeters (mm).
For transporting pallets on the automatic assembly machine or transfer machine, which requires the highest precision in moving and stopping pallets in position, each of the pallets contains an indexing device, all of which are driven by means of a single motor installed on the base machine. Then, each of the indexing devices on the pallets engages a transfer bar and chain, which is driven intermittently by the indexing device to cause the pallet to travel on a usually straight-line run way (British Pat. No. 1557542).
In another conventional pallet transport which is known as a free-flow transport system, pallets are carried by a chain, roller conveyer, or belt conveyor, traveling toward a stop position on a run way. At the stop position, each pallet is forced to abut against a stopper in order to bring it to rest. Therefore, the pallet must have a physical impact against the stopper when it is being stopped. This type of pallet transport system cannot accomplish high precision, therefore.